Method for front end of line fabrication

ABSTRACT

In one embodiment, a method for removing native oxides from a substrate surface is provided which includes supporting a substrate containing silicon oxide within a processing chamber, generating a plasma of reactive species from a gas mixture within the processing chamber, cooling the substrate to a first temperature of less than about 65° C. within the processing chamber, and directing the reactive species to the cooled substrate to react with the silicon oxide thereon while forming a film on the substrate. The film usually contains ammonium hexafluorosilicate. The method further provides positioning the substrate in close proximity to a gas distribution plate, and heating the substrate to a second temperature of about 100° C. or greater within the processing chamber to sublimate or remove the film. The gas mixture may contain ammonia, nitrogen trifluoride, and a carrier gas.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 11/137,609, filedMay 24, 2005, now issued as U.S. Pat. No. 7,396,480, which is adivisional of U.S. Ser. No. 11/063,645, filed on Feb. 22, 2005, whichclaims benefit of U.S. Ser. No. 60/547,839, filed Feb. 26, 2004, whichare all herein incorporated by reference in their entirety. Thisapplication is also related to U.S. patent application Ser. No.11/137,199, filed May 24, 2005; U.S. patent application Ser. No.11/266,167, filed Nov. 3, 2005; U.S. patent application Ser. No.11/622,437, filed Jan. 11, 2007; and U.S. patent application Ser. No.11/962,791, filed Dec. 21, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to semiconductorprocessing equipment. More particularly, embodiments of the presentinvention relate to a chemical vapor deposition (CVD) system forsemiconductor fabrication and in situ dry cleaning methods using thesame.

2. Description of the Related Art

A native oxide typically forms when a substrate surface is exposed tooxygen. Oxygen exposure occurs when the substrate is moved betweenprocessing chambers at atmospheric conditions, or when a small amount ofoxygen remaining in a vacuum chamber contacts the substrate surface.Native oxides may also result if the substrate surface is contaminatedduring etching. Native oxides typically form an undesirable film on thesubstrate surface. Native oxide films are usually very thin, such asbetween 5 Å and 20 Å, but thick enough to cause difficulties insubsequent fabrication processes.

Such difficulties usually affect the electrical properties ofsemiconductor devices formed on the substrate. For example, a particularproblem arises when native silicon oxide films are formed on exposedsilicon containing layers, especially during processing of Metal OxideSilicon Field Effect Transistor (“MOSFET”) structures. Silicon oxidefilms are electrically insulating and are undesirable at interfaces withcontact electrodes or interconnecting electrical pathways because theycause high electrical contact resistance. In MOSFET structures, theelectrodes and interconnecting pathways include silicide layers formedby depositing a refractory metal on bare silicon and annealing the layerto produce the metal silicide layer. Native silicon oxide films at theinterface between the substrate and the metal reduce the compositionaluniformity of the silicide layer by impeding the diffusional chemicalreaction that forms the metal silicide. This results in lower substrateyields and increased failure rates due to overheating at the electricalcontacts. The native silicon oxide film can also prevent adhesion ofother CVD or sputtered layers which are subsequently deposited on thesubstrate.

Sputter etch processes have been tried to reduce contaminants in largefeatures or in small features having aspect ratios smaller than about4:1. However, sputter etch processes can damage delicate silicon layersby physical bombardment. In response, wet etch processes usinghydrofluoric acid (HF) and deionized water, for example, have also beentried. Wet etch processes such as this, however, are disadvantageous intoday's smaller devices where the aspect ratio exceeds 4:1, andespecially where the aspect ratio exceeds 10:1. Particularly, the wetsolution cannot penetrate into those sizes of vias, contacts, or otherfeatures formed within the substrate surface. As a result, the removalof the native oxide film is incomplete. Similarly, a wet etch solution,if successful in penetrating a feature of that size, is even moredifficult to remove from the feature once etching is complete.

Another approach for eliminating native oxide films is a dry etchprocess, such as one utilizing fluorine-containing gases. Onedisadvantage to using fluorine-containing gases, however, is thatfluorine is typically left behind on the substrate surface. Fluorineatoms or fluorine radicals left behind on the substrate surface can bedetrimental. For example, the fluorine atoms left behind can continue toetch the substrate causing voids therein.

A more recent approach to remove native oxide films has been to form afluorine/silicon-containing salt on the substrate surface that issubsequently removed by thermal anneal. In this approach, a thin layerof the salt is formed by reacting a fluorine-containing gas with thesilicon oxide surface. The salt is then heated to an elevatedtemperature sufficient to dissociate the salt into volatile by-productswhich are then removed from the processing chamber. The formation of areactive fluorine-containing gas is usually assisted by thermal additionor by plasma energy. The salt is usually formed at a reduced temperaturethat requires cooling of the substrate surface. This sequence of coolingfollowed by heating is usually accomplished by transferring thesubstrate from a cooling chamber where the substrate is cooled to aseparate anneal chamber or furnace where the substrate is heated.

For various reasons, this reactive fluorine processing sequence is notdesirable. Namely, wafer throughput is greatly diminished because of thetime involved to transfer the wafer. Also, the wafer is highlysusceptible to further oxidation or other contamination during thetransfer. Moreover, the cost of ownership is doubled because twoseparate chambers are needed to complete the oxide removal process.

There is a need, therefore, for a processing chamber capable of remoteplasma generation, heating and cooling, and thereby capable ofperforming a single dry etch process in a single chamber.

SUMMARY OF THE INVENTION

A method for removing native oxides from a substrate surface isprovided. In at least one embodiment, the method includes supporting thesubstrate surface in a vacuum chamber and generating reactive speciesfrom a gas mixture within the chamber. The substrate surface is thencooled within the chamber and the reactive species are directed to thecooled substrate surface to react with the native oxides thereon andform a film on the substrate surface. The substrate surface is thenheated within the chamber to vaporize or remove the film.

In at least one other embodiment, the method includes generating aplasma of reactive species in a first section of the chamber and coolingthe substrate surface having the native oxides thereon in a secondsection of the chamber. Reactive species from the first section flow tothe second section to react with the cooled substrate surface. A film isdeposited on the cooled substrate surface, and the substrate surface ismoved to a third section of the chamber. The substrate surface is thenheated in the third section of the chamber to sublimate or remove thefilm.

In yet another embodiment, the method includes generating a plasma ofreactive species comprising nitrogen and fluorine atoms, and exposingthe substrate surface to the reactive species. The substrate surface iscooled to a temperature below about 22° C., and a film of the nitrogenand fluorine atoms is deposited on the chilled substrate surface. Thesubstrate surface is annealed to sublimate or remove the film.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1A shows a partial cross sectional view of an illustrativeprocessing chamber 100 for heating, cooling, and etching.

FIG. 1B shows an enlarged schematic view of an illustrative linerdisposed within the processing chamber of FIG. 1A.

FIG. 2A shows an enlarged cross sectional view of an illustrative lidassembly that can be disposed at an upper end of the chamber body shownin FIG. 1A.

FIGS. 2B-2C show enlarged schematic views of the gas distribution plateof FIG. 2A.

FIG. 3A shows a partial cross sectional view of an illustrative supportassembly, which is at least partially disposed within the chamber body112 of FIG. 1A.

FIG. 3B shows an enlarged partial cross sectional view of theillustrative support member 300 of FIG. 3A.

FIG. 4A shows a schematic cross sectional view of another illustrativelid assembly 400.

FIG. 4B shows an enlarged schematic, partial cross sectional view of theupper electrode of FIG. 4A.

FIG. 4C shows a partial cross sectional view of the illustrativeprocessing chamber 100 utilizing the lid assembly 400 of FIG. 4A.

FIGS. 5A-5H are sectional schematic views of a fabrication sequence forforming an illustrative active electronic device, such as a MOSFETstructure.

FIG. 6 is a schematic diagram of an exemplary multi-chamber processingsystem adapted to perform multiple processing operations.

DETAILED DESCRIPTION

A processing chamber for any number of substrate processing techniquesis provided. The chamber is particularly useful for performing a plasmaassisted dry etch process that requires both heating and cooling of thesubstrate surface without breaking vacuum. For example, the processingchamber described herein is envisioned to be best suited for afront-end-of line (FEOL) clean chamber for removing oxides and othercontaminants from a substrate surface.

A “substrate surface,” as used herein, refers to any substrate surfaceupon which processing is performed. For example, a substrate surface mayinclude silicon, silicon oxide, doped silicon, germanium, galliumarsenide, glass, sapphire, and any other materials such as metals, metalnitrides, metal alloys, and other conductive materials, depending on theapplication. A substrate surface may also include dielectric materialssuch as silicon dioxide, organosilicates, and carbon doped siliconoxides. The substrate itself is not limited to any particular size orshape. In one aspect, the term “substrate” refers to a round waferhaving a 200 mm diameter or 300 mm diameter. In another aspect, the term“substrate” refers to any polygonal, squared, rectangular, curved orotherwise non-circular workpiece, such as a glass substrate used in thefabrication of flat panel displays, for example.

FIG. 1A is a partial cross sectional view showing an illustrativeprocessing chamber 100. In one embodiment, the processing chamber 100includes a chamber body 112, a lid assembly 200, and a support assembly300. The lid assembly 200 is disposed at an upper end of the chamberbody 112, and the support assembly 300 is at least partially disposedwithin the chamber body 112. The processing chamber 100 and theassociated hardware are preferably formed from one or moreprocess-compatible materials, such as aluminum, anodized aluminum,nickel plated aluminum, nickel plated aluminum 6061-T6, stainless steel,as well as combinations and alloys thereof, for example.

The chamber body 112 includes a slit valve opening 160 formed in asidewall thereof to provide access to the interior of the processingchamber 100. The slit valve opening 160 is selectively opened and closedto allow access to the interior of the chamber body 112 by a waferhandling robot (not shown). Wafer handling robots are well known tothose with skill in the art, and any suitable robot may be used. Forexample, an exemplary robotic transfer assembly has been described in acommonly assigned U.S. Pat. No. 4,951,601, the complete disclosure ofwhich is incorporated herein by reference. In one embodiment, a wafercan be transported in and out of the processing chamber 100 through theslit valve opening 160 to an adjacent transfer chamber and/or load-lockchamber, or another chamber within a cluster tool. A cluster tool of atype that can be coupled to the processing chamber 100 is described in acommonly assigned U.S. Pat. No. 5,186,718, which is herein incorporatedby reference.

In one or more embodiments, the chamber body 112 includes a channel 113formed therein for flowing a heat transfer fluid therethrough. The heattransfer fluid can be a heating fluid or a coolant and is used tocontrol the temperature of the chamber body 112 during processing andsubstrate transfer. The temperature of the chamber body 112 is importantto prevent unwanted condensation of the gas or byproducts on the chamberwalls. Exemplary heat transfer fluids include water, ethylene glycol, ora mixture thereof. An exemplary heat transfer fluid may also includenitrogen gas.

The chamber body 112 can further include a liner 133 that surrounds thesupport assembly 300. The liner 133 is preferably removable forservicing and cleaning. The liner 133 can be made of a metal such asaluminum, or a ceramic material. However, the liner 133 can be anyprocess compatible material. The liner 133 can be bead blasted toincrease the adhesion of any material deposited thereon, therebypreventing flaking of material which results in contamination of theprocessing chamber 100. In one or more embodiments, the liner 133includes one or more apertures 135 and a pumping channel 129 formedtherein that is in fluid communication with a vacuum system. Theapertures 135 provide a flow path for gases into the pumping channel129, which provides an egress for the gases within the processingchamber 100.

The vacuum system can include a vacuum pump 125 and a throttle valve 127to regulate flow of gases through the processing chamber 100. The vacuumpump 125 is coupled to a vacuum port 131 disposed on the chamber body112 and therefore, in fluid communication with the pumping channel 129formed within the liner 133. The terms “gas” and “gases” are usedinterchangeably, unless otherwise noted, and refer to one or moreprecursors, reactants, catalysts, carrier, purge, cleaning, combinationsthereof, as well as any other fluid introduced into the chamber body112.

Considering the liner 133 in greater detail, FIG. 1B shows an enlargedschematic view of one embodiment of the liner 133. In this embodiment,the liner 133 includes an upper portion 133A and a lower portion 133B.An aperture 133C that aligns with the slit valve opening 160 disposed ona side wall of the chamber body 112 is formed within the liner 133 toallow entry and egress of substrates to/from the chamber body 112.Typically, the pumping channel 129 is formed within the upper portion133A. The upper portion 133A also includes the one or more apertures 135formed therethrough to provide passageways or flow paths for gases intothe pumping channel 129.

Referring to FIGS. 1A-1B, the apertures 135 allow the pumping channel129 to be in fluid communication with a processing zone 140 within thechamber body 112. The processing zone 140 is defined by a lower surfaceof the lid assembly 200 and an upper surface of the support assembly300, and is surrounded by the liner 133. The apertures 135 may beuniformly sized and evenly spaced about the liner 133. However, anynumber, position, size or shape of apertures may be used, and each ofthose design parameters can vary depending on the desired flow patternof gas across the substrate receiving surface as is discussed in moredetail below. In addition, the size, number and position of theapertures 135 are configured to achieve uniform flow of gases exitingthe processing chamber 100. Further, the aperture size and location maybe configured to provide rapid or high capacity pumping to facilitate arapid exhaust of gas from the chamber 100. For example, the number andsize of apertures 135 in close proximity to the vacuum port 131 may besmaller than the size of apertures 135 positioned farther away from thevacuum port 131.

Still referring to FIGS. 1A-1B, the lower portion 133B of the liner 133includes a flow path or vacuum channel 129A disposed therein. The vacuumchannel 129A is in fluid communication with the vacuum system describedabove. The vacuum channel 129A is also in fluid communication with thepumping channel 129 via a recess or port 129B formed in an outerdiameter of the liner 133. Generally, two gas ports 129B (only one shownin this view) are formed in an outer diameter of the liner 133 betweenthe upper portion 133A and the lower portion 133B. The gas ports 129Bprovide a flow path between the pumping channel 129 and the vacuumchannel 129A. The size and location of each port 129B is a matter ofdesign, and are determined by the stoichiometry of a desired film, thegeometry of the device being formed, the volume capacity of theprocessing chamber 100 as well as the capabilities of the vacuum systemcoupled thereto. Typically, the ports 129B are arranged opposite oneanother or 180 degrees apart about the outer diameter of the liner 133.

In operation, one or more gases exiting the processing chamber 100 flowthrough the apertures 135 formed through the upper portion 133A of theliner 133 into the pumping channel 129. The gas then flows within thepumping channel 129 and through the ports 129B into the vacuum channel129A. The gas exits the vacuum channel 129A through the vacuum port 131into the vacuum pump 125.

Considering the lid assembly 200 in more detail, FIG. 2A shows anenlarged cross sectional view of an illustrative lid assembly 200 thatcan be disposed at an upper end of the chamber body 112 shown in FIG.1A. Referring to FIGS. 1A and 2A, the lid assembly 200 includes a numberof components stacked on top of one another, as shown in FIG. 1A. In oneor more embodiments, the lid assembly 200 includes a lid rim 210, gasdelivery assembly 220, and a top plate 250. The gas delivery assembly220 is coupled to an upper surface of the lid rim 210 and is arranged tomake minimum thermal contact therewith. The components of the lidassembly 200 are preferably constructed of a material having a highthermal conductivity and low thermal resistance, such as an aluminumalloy with a highly finished surface for example. Preferably, thethermal resistance of the components is less than about 5×10⁻⁴ m²K/W.The lid rim 210 is designed to hold the weight of the components makingup the lid assembly 200 and is coupled to an upper surface of thechamber body 112 via a hinge assembly (not shown in this view) toprovide access to the internal chamber components, such as the supportassembly 300 for example.

Referring to FIGS. 2B-2C, the gas delivery assembly 220 can include adistribution plate or showerhead 225. FIG. 2B shows an enlargedschematic view of one embodiment of an illustrative gas distributionplate 225 and FIG. 2C shows a partial cross sectional view. In one ormore embodiments, the distribution plate 225 is substantiallydisc-shaped and includes a plurality of apertures 225A or passageways todistribute the flow of gases therethrough. The apertures 225A of thedistribution plate 225 prevent the gases flowing through the lidassembly 200 from impinging directly on the substrate surface below byslowing and re-directing the velocity profile of the flowing gases. Theapertures 225A of the distribution plate 225 also evenly distribute theflow of the gas exiting the lid assembly 200, thereby providing an evendistribution of the gas across the surface of the substrate.

Referring to FIGS. 2A-2C, the distribution plate 225 further includes anannular mounting flange 222 formed at a perimeter thereof, which issized to rest on the lid rim 210. Accordingly, the distribution plate225 makes minimal contact with the lid assembly 200. Preferably, ano-ring type seal 224, such as an elastomeric o-ring, is at leastpartially disposed within the annular mounting flange 222 to ensure afluid-tight contact with the lid rim 210.

The gas delivery assembly 220 can further include a blocker assembly 230disposed adjacent the distribution plate 225. The blocker assembly 230provides an even distribution of gas to the backside of the distributionplate 225. Preferably, the blocker assembly 230 is made of an aluminumalloy and is removably coupled to the distribution plate 225 to ensuregood thermal contact. For example, the blocker assembly 230 can becoupled to the distribution plate 225 using a bolt 221 or similarfastener. Preferably, the blocker assembly 230 makes no thermal contactwith the lid rim 210 as shown in FIG. 2A.

In one or more embodiments, the blocker assembly 230 includes a firstblocker plate 233 mounted to a second blocker plate 235. The secondblocker plate 235 includes a passage 259 formed therethrough.Preferably, the passage 259 is centrally located through the secondblocker plate 235 such that the passage 259 is in fluid communicationwith a first cavity or volume 261 defined by a lower surface of the topplate 250 and an upper surface of the second blocker plate 235. Thepassage 259 is also in fluid communication with a second cavity orvolume 262 defined by a lower surface of the second blocker plate 235and an upper surface of the first blocker plate 233. The passage 259 isalso in fluid communication with a third cavity or volume 263 defined bya lower surface of the first blocker plate 233 and an upper surface ofthe distribution plate 225. The passage 259 is coupled to a gas inlet223. The gas inlet 223 is coupled to the top plate 250 at a first endthereof. Although not shown, the gas inlet 223 is coupled at a secondend thereof to one or more upstream gas sources and/or other gasdelivery components, such as gas mixers.

The first blocker plate 233 includes a plurality of passageways 233Aformed therein that are adapted to disperse the gases flowing from thepassage 259 to the gas distribution plate 225. Although the passageways233A are shown as being circular or rounded, the passageways 233A can besquare, rectangular, or any other shape. The passageways 233A can besized and positioned about the blocker plate 233 to provide a controlledand even flow distribution across the surface of the substrate. Asdescribed above, the first blocker plate 233 can easily be removed fromthe second blocker plate 235 and from the distribution plate 225 tofacilitate cleaning or replacement of those components.

In use, one or more process gases are introduced into the gas deliveryassembly 220 via the gas inlet 223. The process gas flows into the firstvolume 261 and through the passage 259 of the second blocker plate 235into the second volume 262. The process gas is then distributed throughthe holes 233A of the first blocker plate 233 into the third volume 263and further distributed through the holes 225A of the distribution plate225 until the gas meets the exposed surfaces of the substrate disposedwithin the chamber body 112.

A gas supply panel (not shown) is typically used to provide the one ormore gases to the processing chamber 100. The particular gas or gasesthat are used depend upon the process or processes to be performedwithin the chamber 100. Illustrative gases can include, but are notlimited to one or more precursors, reductants, catalysts, carriers,purge, cleaning, or any mixture or combination thereof. Typically, theone or more gases introduced to the processing chamber 100 flow throughthe inlet 223 into the lid assembly 200 and then into the chamber body112 through the gas delivery assembly 220. An electronically operatedvalve and/or flow control mechanism (not shown) may be used to controlthe flow of gas from the gas supply into the processing chamber 100.Depending on the process, any number of gases can be delivered to theprocessing chamber 100, and can be mixed either in the processingchamber 100 or before the gases are delivered to the processing chamber100, such as within a gas mixture (not shown), for example.

Still referring to FIGS. 1A and 2A, the lid assembly 200 can furtherinclude an electrode 240 to generate a plasma of reactive species withinthe lid assembly 200. In one embodiment, the electrode 240 is supportedon the top plate 250 and is electrically isolated therefrom. Forexample, an isolator filler ring 241 can be disposed about a lowerportion of the electrode 240 separating the electrode 240 from the topplate 250 as shown in FIG. 2A. An annular isolator 242 can also bedisposed about an outer surface of the isolator filler ring 241. Anannular insulator 243 can then be disposed about an upper portion of theelectrode 240 so that the electrode 240 is electrically isolated fromthe top plate 250 and all the other components of the lid assembly 200.Each of these rings 241, 242, 243 can be made from aluminum oxide or anyother insulative, process compatible material.

In one or more embodiments, the electrode 240 is coupled to a powersource (not shown) while the gas delivery assembly 220 is connected toground (e.g., the gas delivery assembly 220 serves as an electrode).Accordingly, a plasma of one or more process gases can be generated inthe volumes 261, 262 and/or 263 between the electrode 240 (“firstelectrode”) and the gas delivery assembly 220 (“second electrode”). Forexample, the plasma can be struck and contained between the electrode240 and the blocker assembly 230. Alternatively, the plasma can bestruck and contained between the electrode 240 and the distributionplate 225, in the absence of the blocker assembly 230. In eitherembodiment, the plasma is well confined or contained within the lidassembly 200. Accordingly, the plasma is a “remote plasma” since noactive plasma is in direct contact with the substrate disposed withinthe chamber body 112. As a result, plasma damage to the substrate isavoided because the plasma is sufficiently separated from the substratesurface.

Any power source capable of activating the gases into reactive speciesand maintaining the plasma of reactive species may be used. For example,radio frequency (RF), direct current (DC), or microwave (MW) based powerdischarge techniques may be used. The activation may also be generatedby a thermally based technique, a gas breakdown technique, a highintensity light source (e.g., UV energy), or exposure to an x-raysource. Alternatively, a remote activation source may be used, such as aremote plasma generator, to generate a plasma of reactive species whichare then delivered into the chamber 100. Exemplary remote plasmagenerators are available from vendors such as MKS Instruments, Inc. andAdvanced Energy Industries, Inc. Preferably, an RF power supply iscoupled to the electrode 240.

Referring to FIG. 2A, the gas delivery assembly 220 can be heateddepending on the process gases and operations to be performed within theprocessing chamber 100. In one embodiment, a heating element 270, suchas a resistive heater for example, can be coupled to the distributionplate 225. In one embodiment, the heating element 270 is a tubularmember and is pressed into an upper surface of the distribution plate225 as shown in more detail in FIGS. 2B-2C.

Referring to FIGS. 2B-2C, the upper surface of the distribution plate225 includes a groove or recessed channel having a width slightlysmaller than the outer diameter of the heating element 270, such thatthe heating element 270 is held within the groove using an interferencefit. The heating element 270 regulates the temperature of the gasdelivery assembly 220 since the components of the delivery assembly 220,including the distribution plate 225 and the blocker assembly 230, areeach conductively coupled to one another. Regulation of the temperaturemay be facilitated by a thermocouple 272 coupled to the distributionplate 225. The thermocouple 272 may be used in a feedback loop tocontrol electric current applied to the heating element 270 from a powersupply, such that the gas delivery assembly 220 temperature can bemaintained or controlled at a desired temperature or within a desiredtemperature range. Control of the gas delivery assembly 220 temperatureis facilitated because as described above, the gas delivery assembly 220makes minimal thermal contact with the other components of the lidassembly 200, and as such, thermal conductivity is limited.

In one or more embodiments, the lid assembly 200 can include one or morefluid channel 202 formed therein for flowing a heat transfer medium toprovide temperature control of the gas delivery assembly 220. In oneembodiment, the fluid channel 202 can be formed within the lid rim 210,as shown in FIG. 2A. Alternatively, the fluid channel 202 can be formedwithin any component of the lid assembly 200 to provide an uniform heattransfer to the gas delivery assembly 220. The fluid channel 202 cancontain either a heating or cooling medium to control temperature of thegas delivery assembly 220, depending on the process requirements withinthe chamber 100. Any heat transfer medium may be used, such as nitrogen,water, ethylene glycol, or mixtures thereof, for example.

In one or more embodiments, the gas delivery assembly 220 can be heatedusing one or more heat lamps (not shown). Typically, the heat lamps arearranged about an upper surface of the distribution plate 225 to heatthe distribution plate 225 by radiation.

FIG. 3A shows a partial cross sectional view of an illustrative supportassembly 300. The support assembly 300 can be at least partiallydisposed within the chamber body 112. The support assembly 300 caninclude a support member 310 to support a substrate (not shown in thisview) for processing within the chamber body 112. The support member 310can be coupled to a lift mechanism 330 through a shaft 314 which extendsthrough a centrally-located opening 114 formed in a bottom surface ofthe chamber body 112. The lift mechanism 330 can be flexibly sealed tothe chamber body 112 by a bellows 333 that prevents vacuum leakage fromaround the shaft 314. The lift mechanism 330 allows the support member310 to be moved vertically within the chamber body 112 between a processposition and a lower, transfer position. The transfer position isslightly below the opening of the slit valve 160 formed in a sidewall ofthe chamber body 112.

FIG. 3B shows an enlarged partial cross sectional of the supportassembly 300 shown in FIG. 3A. In one or more embodiments, the supportmember 310 has a flat, circular surface or a substantially flat,circular surface for supporting a substrate to be processed thereon. Thesupport member 310 is preferably constructed of aluminum. The supportmember 310 can include a removable top plate 311 made of some othermaterial, such as silicon or ceramic material, for example, to reducebackside contamination of the substrate.

In one or more embodiments, the support member 310 or the top plate 311can include a plurality of extensions or dimples 311A arranged on theupper surface thereof. In FIG. 3B, the dimples 311A are shown on theupper surface of the top plate 311. It can be envisioned that thedimples 311A can be arranged on the upper surface of the support member310 if a top plate 311 is not desired. The dimples 311A provide minimumcontact between the lower surface of the substrate and the supportsurface of the support assembly 300 (e.g. either the support member 310or the top plate 311).

In one or more embodiments, the substrate (not shown) may be secured tothe support assembly 300 using a vacuum chuck. The top plate 311 caninclude a plurality of holes 312 in fluid communication with one or moregrooves 316 formed in the support member 310. The grooves 316 are influid communication with a vacuum pump (not shown) via a vacuum conduit313 disposed within the shaft 314 and the support member 310. Undercertain conditions, the vacuum conduit 313 can be used to supply a purgegas to the surface of the support member 310 to prevent deposition whena substrate is not disposed on the support member 310. The vacuumconduit 313 can also pass a purge gas during processing to prevent areactive gas or byproduct from contacting the backside of the substrate.

In one or more embodiments, the substrate (not shown) may be secured tothe support member 310 using an electrostatic chuck. In one or moreembodiments, the substrate can be held in place on the support member310 by a mechanical clamp (not shown), such as a conventional clampring.

Preferably, the substrate is secured using an electrostatic chuck. Anelectrostatic chuck typically includes at least a dielectric materialthat surrounds an electrode (not shown), which may be located on anupper surface of the support member 310 or formed as an integral part ofthe support member 310. The dielectric portion of the chuck electricallyinsulates the chuck electrode from the substrate and from the remainderof the support assembly 300.

In one or more embodiments, the perimeter of the chuck dielectric can beis slightly smaller than the perimeter of the substrate. In other words,the substrate slightly overhangs the perimeter of the chuck dielectricso that the chuck dielectric will remain completely covered by thesubstrate even if the substrate is misaligned off center when positionedon the chuck. Assuring that the substrate completely covers the chuckdielectric ensures that the substrate shields the chuck from exposure topotentially corrosive or damaging substances within the chamber body112.

The voltage for operating the electrostatic chuck can be supplied by aseparate “chuck” power supply (not shown). One output terminal of thechucking power supply is connected to the chuck electrode. The otheroutput terminal typically is connected to electrical ground, butalternatively may be connected to a metal body portion of the supportassembly 300. In operation, the substrate is placed in contact with thedielectric portion, and a direct current voltage is placed on theelectrode to create the electrostatic attractive force or bias to adherethe substrate on the upper surface of the support member 310.

Still referring to FIGS. 3A-3B, the support member 310 can include oneor more bores 323 formed therethrough to accommodate a lift pin 325.Each lift pin 325 is typically constructed of ceramic orceramic-containing materials, and are used for substrate-handling andtransport. Each lift pin 325 is slideably mounted within the bore 323.In one aspect, the bore 323 is lined with a ceramic sleeve to helpfreely slide the lift pin 325. The lift pin 325 is moveable within itsrespective bore 323 by engaging an annular lift ring 320 disposed withinthe chamber body 112. The lift ring 320 is movable such that the uppersurface of the lift-pin 325 can be located above the substrate supportsurface of the support member 310 when the lift ring 320 is in an upperposition. Conversely, the upper surface of the lift-pins 325 is locatedbelow the substrate support surface of the support member 310 when thelift ring 320 is in a lower position. Thus, part of each lift-pin 325passes through its respective bore 323 in the support member 310 whenthe lift ring 320 moves from either the lower position to the upperposition.

When activated, the lift pins 325 push against a lower surface of thesubstrate, lifting the substrate off the support member 310. Conversely,the lift pins 325 may be de-activated to lower the substrate, therebyresting the substrate on the support member 310. The lift pins 325 caninclude enlarged upper ends or conical heads to prevent the pins 325from falling out from the support member 310. Other pin designs can alsobe utilized and are well known to those skilled in the art.

In one embodiment, one or more of the lift pins 325 include a coating oran attachment disposed thereon that is made of a non-skid or highlyfrictional material to prevent the substrate from sliding when supportedthereon. A preferred material is a high temperature, polymeric materialthat does not scratch or otherwise damage the backside of the substratewhich would create contaminants within the processing chamber 100.Preferably, the coating or attachment is KALREZ® coating available fromDuPont Co.

To drive the lift ring 320, an actuator, such as a conventionalpneumatic cylinder or a stepper motor (not shown), is generally used.The stepper motor or cylinder drives the lift ring 320 in the up or downpositions, which in turn drives the lift-pins 325 that raise or lowerthe substrate. In a specific embodiment, a substrate (not shown) issupported on the support member 310 by three lift-pins 325 (not shown inthis view) dispersed approximately 120 degrees apart and projecting fromthe lift ring 320.

Referring again to FIG. 3A, the support assembly 300 can include an edgering 305 disposed about the support member 310. The edge ring 305 can bemade of a variety of materials such as ceramic, quartz, aluminum, andsteel, among others. In one or more embodiments, the edge ring 305 is anannular member that is adapted to cover an outer perimeter of thesupport member 310 and protect the support member 310 from deposition.The edge ring 305 can be positioned on or adjacent the support member310 to form an annular purge gas channel 334 between the outer diameterof support member 310 and the inner diameter of the edge ring 305. Theannular purge gas channel 334 can be in fluid communication with a purgegas conduit 335 formed through the support member 310 and the shaft 314.Preferably, the purge gas conduit 335 is in fluid communication with apurge gas supply (not shown) to provide a purge gas to the purge gaschannel 334. Any suitable purge gas such as nitrogen, argon, or helium,may be used alone or in combination. In operation, the purge gas flowsthrough the conduit 335, into the purge gas channel 334, and about anedge of the substrate disposed on the support member 310. Accordingly,the purge gas working in cooperation with the edge ring 305 preventsdeposition at the edge and/or backside of the substrate.

Referring again to FIGS. 3A-3B, the temperature of the support assembly300 is controlled by a fluid circulated through a fluid channel 360embedded in the body of the support member 310. In one or moreembodiments, the fluid channel 360 is in fluid communication with a heattransfer conduit 361 disposed through the shaft 314 of the supportassembly 300. Preferably, the fluid channel 360 is positioned about thesupport member 310 to provide a uniform heat transfer to the substratereceiving surface of the support member 310. The fluid channel 360 andheat transfer conduit 361 can flow heat transfer fluids to either heator cool the support member 310. Any suitable heat transfer fluid may beused, such as water, nitrogen, ethylene glycol, or mixtures thereof. Thesupport assembly 300 can further include an embedded thermocouple (notshown) for monitoring the temperature of the support surface of thesupport member 310. For example, a signal from the thermocouple may beused in a feedback loop to control the temperature or flowrate of thefluid circulated through the fluid channel 360.

Referring back to FIG. 3A, the support member 310 can be movedvertically within the chamber body 112 so that a distance betweensupport member 310 and the lid assembly 200 can be controlled. A sensor(not shown) can provide information concerning the position of supportmember 310 within chamber 100. An example of a lifting mechanism for thesupport member 310 is described in detail in U.S. Pat. No. 5,951,776,which is hereby incorporated by reference in its entirety.

In operation, the support member 310 can be elevated to a closeproximity of the lid assembly 200 to control the temperature of thesubstrate being processed. As such, the substrate can be heated viaradiation emitted from the distribution plate 225 that is controlled bythe heating element 270. Alternatively, the substrate can be lifted offthe support member 310 to close proximity of the heated lid assembly 200using the lift pins 325 activated by the lift ring 320.

After extended periods of use or at designated times for scheduledmaintenance, certain components of the processing chamber 100 includingthose described above can be regularly inspected, replaced, or cleaned.These components are typically parts that are collectively known as the“process kit.” Illustrative components of the process kit can include,but are not limited to the showerhead 225, the top plate 311, the edgering 305, the liner 133, and the lift pins 325, for example. Any one ormore of these components are typically removed from the chamber 100 andcleaned or replaced at regular intervals or according to an as-neededbasis.

FIG. 4A shows a partial cross sectional view of another illustrative lidassembly 400. The lid assembly 400 includes at least two stackedcomponents configured to form a plasma volume or cavity therebetween. Inone or more embodiments, the lid assembly 400 includes a first electrode410 (“upper electrode”) disposed vertically above a second electrode 450(“lower electrode”) confining a plasma volume or cavity 425therebetween. The first electrode 410 is connected to a power source415, such as an RF power supply, and the second electrode 450 isconnected to ground, forming a capacitance between the two electrodes410, 450.

In one or more embodiments, the lid assembly 400 includes one or moregas inlets 412 (only one is shown) that are at least partially formedwithin an upper section 413 of the first electrode 410. The one or moreprocess gases enter the lid assembly 400 via the one or more gas inlets412. The one or more gas inlets 412 are in fluid communication with theplasma cavity 425 at a first end thereof and coupled to one or moreupstream gas sources and/or other gas delivery components, such as gasmixers, at a second end thereof. The first end of the one or more gasinlets 412 can open into the plasma cavity 425 at the upper most pointof the inner diameter 430 of the expanding section 420 as shown in FIG.4A. Similarly, the first end of the one or more gas inlets 412 can openinto the plasma cavity 425 at any height interval along the innerdiameter 430 of the expanding section 420. Although not shown, two gasinlets 412 can be disposed at opposite sides of the expanding section420 to create a swirling flow pattern or “vortex” flow into theexpanding section 420 which helps mix the gases within the plasma cavity425. A more detailed description of such a flow pattern and gas inletarrangements is provided by commonly assigned U.S. Pat. No. 6,916,398,which is incorporated herein by reference in its entirety.

In one or more embodiments, the first electrode 410 has an expandingsection 420 that houses the plasma cavity 425. As shown in FIG. 4A, theexpanding section 420 is in fluid communication with the gas inlet 412as described above. In one or more embodiments, the expanding section420 is an annular member that has an inner surface or diameter 430 thatgradually increases from an upper portion 420A thereof to a lowerportion 420B thereof. As such, the distance between the first electrode410 and the second electrode 450 is variable. That varying distancehelps control the formation and stability of the plasma generated withinthe plasma cavity 425.

In one or more embodiments, the expanding section 420 resembles a coneor “funnel,” as is shown in FIGS. 4A-4B. FIG. 4B shows an enlargedschematic, partial cross sectional view of the upper electrode of FIG.4A. In one or more embodiments, the inner surface 430 of the expandingsection 420 gradually slopes from the upper portion 420A to the lowerportion 420B of the expanding section 420. The slope or angle of theinner diameter 430 can vary depending on process requirements and/orprocess limitations. The length or height of the expanding section 420can also vary depending on specific process requirements and/orlimitations. In one or more embodiments, the slope of the inner diameter430, or the height of the expanding section 420, or both can varydepending on the volume of plasma needed for processing. For example,the slope of the inner diameter 430 can be at least 1:1, or at least1.5:1 or at least 2:1 or at least 3:1 or at least 4:1 or at least 5:1 orat least 10:1. In one or more embodiments, the slope of the innerdiameter 430 can range from a low of 2:1 to a high of 20:1.

In one or more embodiments, the expanding section 420 can be curved orarced although not shown in the figures. For example, the inner surface430 of the expanding section 420 can be curved or arced to be eitherconvexed or concaved. In one or more embodiments, the inner surface 430of the expanding section 420 can have a plurality of sections that areeach sloped, tapered, convexed, or concaved.

As mentioned above, the expanding section 420 of the first electrode 410varies the vertical distance between the first electrode 410 and thesecond electrode 450 because of the gradually increasing inner surface430 of the first electrode 410. That variable distance is directlyrelated to the power level within the plasma cavity 425. Not wishing tobe bound by theory, the variation in distance between the two electrodes410, 450 allows the plasma to find the necessary power level to sustainitself within some portion of the plasma cavity 425 if not throughoutthe entire plasma cavity 425. The plasma within the plasma cavity 425 istherefore less dependent on pressure, allowing the plasma to begenerated and sustained within a wider operating window. As such, a morerepeatable and reliable plasma can be formed within the lid assembly400.

The first electrode 410 can be constructed from any process compatiblematerials, such as aluminum, anodized aluminum, nickel plated aluminum,nickel plated aluminum 6061-T6, stainless steel as well as combinationsand alloys thereof, for example. In one or more embodiments, the entirefirst electrode 410 or portions thereof are nickel coated to reduceunwanted particle formation. Preferably, at least the inner surface 430of the expanding section 420 is nickel plated.

The second electrode 450 can include one or more stacked plates. Whentwo or more plates are desired, the plates should be in electricalcommunication with one another. Each of the plates should include aplurality of apertures or gas passages to allow the one or more gasesfrom the plasma cavity 425 to flow through.

Referring to FIG. 4B, the lid assembly 400 can further include anisolator ring 440 to electrically isolate the first electrode 410 fromthe second electrode 450. The isolator ring 440 can be made fromaluminum oxide or any other insulative, process compatible material.Preferably, the isolator ring 440 surrounds or substantially surroundsat least the expanding section 420 as shown in FIG. 4B.

Referring again to the specific embodiment shown in FIG. 4A, the secondelectrode 450 includes a top plate 460, distribution plate 470 andblocker plate 480. The top plate 460, distribution plate 470 and blockerplate 480 are stacked and disposed on a lid rim 490 which is connectedto the chamber body 112 as shown in FIG. 4B. As is known in the art, ahinge assembly (not shown) can be used to couple the lid rim 490 to thechamber body 112. The lid rim 490 can include an embedded channel orpassage 492 for housing a heat transfer medium. The heat transfer mediumcan be used for heating, cooling, or both, depending on the processrequirements. Illustrative heat transfer mediums are listed above.

In one or more embodiments, the top plate 460 includes a plurality ofgas passages or apertures 465 formed beneath the plasma cavity 425 toallow gas from the plasma cavity 425 to flow therethrough. In one ormore embodiments, the top plate 460 can include a recessed portion 462that is adapted to house at least a portion of the first electrode 410.In one or more embodiments, the apertures 465 are through the crosssection of the top plate 460 beneath the recessed portion 462. Therecessed portion 462 of the top plate 460 can be stair stepped as shownin FIG. 4A to provide a better sealed fit therebetween. Furthermore, theouter diameter of the top plate 460 can be designed to mount or rest onan outer diameter of the distribution plate 470 as shown in FIG. 4A. Ano-ring type seal, such as an elastomeric o-ring 463, can be at leastpartially disposed within the recessed portion 462 of the top plate 460to ensure a fluid-tight contact with the first electrode 410. Likewise,an o-ring type seal 466 can be used to provide a fluid-tight contactbetween the outer perimeters of the top plate 460 and the distributionplate 470.

In one or more embodiments, the distribution plate 470 is identical tothe distribution plate 225 shown and described above with reference toFIGS. 2A-2C. Particularly, the distribution plate 470 is substantiallydisc-shaped and includes a plurality of apertures 475 or passageways todistribute the flow of gases therethrough. The apertures 475 can besized and positioned about the distribution plate 470 to provide acontrolled and even flow distribution to the chamber body 112 where thesubstrate to be processed is located. Furthermore, the apertures 475prevent the gas(es) from impinging directly on the substrate surface byslowing and re-directing the velocity profile of the flowing gases, aswell as evenly distributing the flow of gas to provide an evendistribution of gas across the surface of the substrate.

The distribution plate 470 can also include an annular mounting flange472 formed at an outer perimeter thereof. The mounting flange 472 can besized to rest on an upper surface of the lid rim 490. An o-ring typeseal, such as an elastomeric o-ring, can be at least partially disposedwithin the annular mounting flange 472 to ensure a fluid-tight contactwith the lid rim 490.

In one or more embodiments, the distribution plate 470 includes one ormore embedded channels or passages 474 for housing a heater or heatingfluid to provide temperature control of the lid assembly 400. Similar tothe lid assembly 200 described above, a resistive heating element can beinserted within the passage 474 to heat the distribution plate 470. Athermocouple can be connected to the distribution plate 470 to regulatethe temperature thereof. The thermocouple can be used in a feedback loopto control electric current applied to the heating element, as describedabove.

Alternatively, a heat transfer medium can be passed through the passage474. The one or more passages 474 can contain a cooling medium, ifneeded, to better control temperature of the distribution plate 470depending on the process requirements within the chamber body 112. Asmentioned above, any heat transfer medium may be used, such as nitrogen,water, ethylene glycol, or mixtures thereof, for example.

In one or more embodiments, the lid assembly 400 can be heated using oneor more heat lamps (not shown). Typically, the heat lamps are arrangedabout an upper surface of the distribution plate 470 to heat thecomponents of the lid assembly 400 including the distribution plate 470by radiation.

The blocker plate 480 is optional and would be disposed between the topplate 460 and the distribution plate 470. Preferably, the blocker plate480 is removably mounted to a lower surface of the top plate 460. Theblocker plate 480 should make good thermal and electrical contact withthe top plate 460. In one or more embodiments, the blocker plate 480 canbe coupled to the top plate 460 using a bolt or similar fastener. Theblocker plate 480 can also be threaded or screwed onto an out diameterof the top plate 460.

The blocker plate 480 includes a plurality of apertures 485 to provide aplurality of gas passages from the top plate 460 to the distributionplate 470. The apertures 485 can be sized and positioned about theblocker plate 480 to provide a controlled and even flow distribution thedistribution plate 470.

FIG. 4C shows a partial cross sectional view of the chamber body 112having the lid assembly 400 disposed thereon. Preferably, the expandingsection 420 is centered above the support assembly 300 as shown in FIG.4C. The confinement of the plasma within the plasma cavity 425 and thecentral location of the confined plasma allows an even and repeatabledistribution of the disassociated gas(es) into the chamber body 112.Particularly, the gas leaving the plasma volume 425 flows through theapertures 465 of the top plate 460 to the upper surface of the blockerplate 480. The apertures 485 of the blocker plate 480 distribute the gasto the backside of the distribution plate 470 where the gas is furtherdistributed through the apertures 475 of the distribution plate 470before contacting the substrate (not shown) within the chamber body 112.

It is believed that the confinement of the plasma within the centrallylocated plasma cavity 425 and the variable distance between the firstelectrode 410 and the second electrode 450 generate a stable andreliable plasma within the lid assembly 400.

For simplicity and ease of description, an exemplary dry etch processfor removing silicon oxide using an ammonia (NH₃) and nitrogentrifluoride (NF₃) gas mixture performed within the processing chamber100 will now be described. It is believed that the processing chamber100 is advantageous for any dry etch process that benefits from a plasmatreatment in addition to both substrate heating and cooling all within asingle processing environment, including an anneal process.

Referring to FIG. 1, the dry etch process begins by placing a substrate(not shown), such as a semiconductor substrate for example, into theprocessing chamber 100. The substrate is typically placed into thechamber body 112 through the slit valve opening 160 and disposed on theupper surface of the support member 310. The substrate is chucked to theupper surface of the support member 310, and an edge purge is passedthrough the channel 334. Preferably, the substrate is chucked to theupper surface of the support member 310 by pulling a vacuum through theholes 312 and grooves 316 that are in fluid communication with a vacuumpump via conduit 313. The support member 310 is then lifted to aprocessing position within the chamber body 112, if not already in aprocessing position. The chamber body 112 is preferably maintained at atemperature of between 50° C. and 80° C., more preferably at about 65°C. This temperature of the chamber body 112 is maintained by passing aheat transfer medium through the fluid channel 113.

The substrate is cooled below 65° C., such as between 15° C. and 50° C.,by passing a heat transfer medium or coolant through the fluid channel360 formed within the support assembly 300. In one embodiment, thesubstrate is maintained below room temperature. In another embodiment,the substrate is maintained at a temperature of between 22° C. and 40°C. Typically, the support member 310 is maintained below about 22° C. toreach the desired substrate temperatures specified above. To cool thesupport member 310, the coolant is passed through the fluid channel 360.A continuous flow of coolant is preferred to better control thetemperature of the support member 310. The coolant is preferably 50percent by volume ethylene glycol and 50 percent by volume water. Ofcourse, any ratio of water and ethylene glycol can be used so long asthe desired temperature of the substrate is maintained.

The ammonia and nitrogen trifluoride gases are then introduced into thechamber 100 to form a cleaning gas mixture. The amount of each gasintroduced into the chamber is variable and may be adjusted toaccommodate, for example, the thickness of the oxide layer to beremoved, the geometry of the substrate being cleaned, the volumecapacity of the plasma, the volume capacity of the chamber body 112, aswell as the capabilities of the vacuum system coupled to the chamberbody 112. In one aspect, the gases are added to provide a gas mixturehaving at least a 1:1 molar ratio of ammonia to nitrogen trifluoride. Inanother aspect, the molar ratio of the gas mixture is at least about 3to 1 (ammonia to nitrogen trifluoride). Preferably, the gases areintroduced in the chamber 100 at a molar ratio of from 5:1 (ammonia tonitrogen trifluoride) to 30:1. More preferably, the molar ratio of thegas mixture is of from about 5 to 1 (ammonia to nitrogen trifluoride) toabout 10 to 1. The molar ratio of the gas mixture may also fall betweenabout 10:1 (ammonia to nitrogen trifluoride) and about 20:1.

A purge gas or carrier gas may also be added to the gas mixture. Anysuitable purge/carrier gas may be used, such as argon, helium, hydrogen,nitrogen, or mixtures thereof, for example. Typically, the overall gasmixture is from about 0.05% to about 20% by volume of ammonia andnitrogen trifluoride. The remainder being the carrier gas. In oneembodiment, the purge or carrier gas is first introduced into thechamber body 112 before the reactive gases to stabilize the pressurewithin the chamber body 112.

The operating pressure within the chamber body 112 can be variable.Typically, the pressure is maintained between about 500 milliTorr andabout 30 Torr. Preferably, the pressure is maintained between about 1Torr and about 10 Torr. More preferably, the operating pressure withinthe chamber body 112 is maintained between about 3 Torr and about 6Torr.

An RF power of from about 5 watts and about 600 watts is applied to theelectrode 240 to ignite a plasma of the gas mixture within the volumes261, 262, and 263 contained in the gas delivery assembly 220.Preferably, the RF power is less than 100 watts. More preferable is thatthe frequency at which the power is applied is very low, such as lessthan 100 kHz. Preferably, the frequency ranges from about 50 kHz toabout 90 kHz.

The plasma energy dissociates the ammonia and nitrogen trifluoride gasesinto reactive species that combine to form a highly reactive ammoniumfluoride (NH₄F) and/or ammonium hydrogen fluoride (NH₄·HF₂) in the gasphase. These molecules then flow through the gas delivery assembly 220via the holes 225A of the distribution plate 225 to react with thesubstrate surface to be cleaned. In one embodiment, the carrier gas isfirst introduced into the chamber 100, a plasma of the carrier gas isgenerated, and then the reactive gases, ammonia and nitrogentrifluoride, are added to the plasma.

Not wishing to be bound by theory, it is believed that the etchant gas,NH₄F and/or NH₄.HF₂, reacts with the silicon oxide surface to formammonium hexafluorosilicate (NH₄)₂SiF₆, NH₃, and H₂O as products. TheNH₃ and H₂O are vapors at processing conditions and removed from thechamber 100 by the vacuum pump 125. In particular, the volatile gasesflow through the apertures 135 formed in the liner 133 into the pumpingchannel 129 before the gases exit the chamber 100 through the vacuumport 131 into the vacuum pump 125. A thin film of (NH₄)₂SiF₆ is leftbehind on the substrate surface. This reaction mechanism can besummarized as follows:NF₃+NH₃→NH₄F+NH₄.HF₂+N₂NH₄F+SiO₂→(NH₄)₂SiF₆+H₂O(NH₄)₂SiF₆+heat→NH₃+HF+SiF₄

After the thin film is formed on the substrate surface, the supportmember 310 having the substrate supported thereon is elevated to ananneal position in close proximity to the heated distribution plate 225.The heat radiated from the distribution plate 225 should be sufficientto dissociate or sublimate the thin film of (NH₄)₂SiF₆ into volatileSiF₄, NH₃, and HF products. These volatile products are then removedfrom the chamber 100 by the vacuum pump 125 as described above.Typically, a temperature of 75° C. or more is used to effectivelysublimate and remove the thin film from the substrate. Preferably, atemperature of 100° C. or more is used, such as between about 115° C.and about 200° C.

The thermal energy to dissociate the thin film of (NH₄)₂SiF₆ into itsvolatile components is convected or radiated by the distribution plate225. As described above, a heating element 270 is directly coupled tothe distribution plate 225, and is activated to heat the distributionplate 225 and the components in thermal contact therewith to atemperature between about 75° C. and 250° C. In one aspect, thedistribution plate 225 is heated to a temperature of between 100° C. and150° C., such as about 120° C.

This elevation change can be effectuated various ways. For example, thelift mechanism 330 can elevate the support member 310 toward a lowersurface of the distribution plate 225. During this lifting step, thesubstrate is secured to the support member 310, such as by the vacuumchuck or electrostatic chuck described above. Alternatively, thesubstrate can be lifted off the support member 310 and placed in closeproximity to the heated distribution plate 225 by elevating the liftpins 325 via the lift ring 320.

The distance between the upper surface of the substrate having the thinfilm thereon and the distribution plate 225 is not critical and is amatter of routine experimentation. A person of ordinary skill in the artcan easily determine the spacing required to efficiently and effectivelyvaporize the thin film without damaging the underlying substrate. It isbelieved, however, that a spacing of between about 0.254 mm (10 mils)and 5.08 mm (200 mils) is effective.

Once the film has been removed from the substrate, the chamber is purgedand evacuated. The cleaned substrate is then removed from the chamberbody 112 by lowering the substrate to the transfer position, de-chuckingthe substrate, and transferring the substrate through the slit valveopening 160.

A system controller (not shown) can be used to regulate the operationsof the processing chamber 100. The system controller can operate underthe control of a computer program stored on a hard disk drive of acomputer. For exemplary, the computer program can dictate the processsequencing and timing, mixture of gases, chamber pressures, RF powerlevels, susceptor positioning, slit valve opening and closing, wafercooling and other parameters of a particular process. The interfacebetween a user and the system controller can be made via a CRT monitorand light pen (not shown). In a preferred embodiment, two monitors areused, one monitor mounted in the clean room wall for the operators andthe other monitor behind the wall for the service technicians. Alsopreferred is that both monitors simultaneously display the sameinformation but only one light pen is enabled. The light pen detectslight emitted by the CRT display with a light sensor in the tip of thepen. To select a particular screen or function, the operator can touch adesignated area of the display screen and push the button on the pen.The display screen generally confirms communication between the lightpen and the touched area by changing its appearance, e.g. highlight orcolor, or displaying a new menu or screen.

A variety of processes can be implemented using a computer programproduct that runs on, for example, the system controller. The computerprogram code can be written in any conventional computer readableprogramming language such as for example 68000 assembly language, C,C++, or PASCAL. Suitable program code can be entered into a single file,or multiple files, using a conventional text editor, and stored orembodied in a computer usable medium, such as a memory system of thecomputer. If the entered code text is in a high level language, the codeis compiled, and the resultant compiler code is then linked with anobject code of precompiled library routines. To execute the linkedcompiled object code, the system user invokes the object code, causingthe computer system to load the code in memory, from which the CPU readsand executes the code to perform the tasks identified in the program.

FIGS. 5A-5H are sectional schematic views of an exemplary fabricationsequence for forming an exemplary active electronic device, such as aMOSFET structure 500, utilizing the dry etch process and the processingchamber 100 described herein. Referring to FIGS. 5A-5H, the exemplaryMOSFET structure may be formed on a semiconductor material, for examplea silicon or gallium arsenide substrate 525. Preferably, the substrate525 is a silicon wafer having a <100> crystallographic orientation and adiameter of 150 mm (6 inches), 200 mm (8 inches), or 300 mm (12 inches).Typically, the MOSFET structure includes a combination of (i) dielectriclayers, such as silicon dioxide, organosilicate, carbon doped siliconoxide, phosphosilicate glass (PSG), borophosphosilicate glass (BPSG),silicon nitride, or combinations thereof; (ii) semiconducting layerssuch as doped polysilicon, and n-type or p-type doped monocrystallinesilicon; and (iii) electrical contacts and interconnect lines formedfrom layers of metal or metal silicide, such as tungsten, tungstensilicide, titanium, titanium silicide, cobalt silicide, nickel silicide,or combinations thereof.

Referring to FIG. 5A, fabrication of the active electronic device beginsby forming electrical isolation structures that electrically isolate theactive electronic device from other devices. There are several types ofelectrical isolation structures as generally described in VLSITechnology, Second Edition, Chapter 11, by S. M. Sze, McGraw-HillPublishing Company (1988), which is incorporated herein by reference. Inone version, a field oxide layer (not shown) having a thickness of about2,000 Å is first grown over the entire substrate 525, and portions ofthe oxide layer are removed to form the field oxide barriers 545A,Bwhich surround exposed regions in which the electrically active elementsof the device are formed. The exposed regions are thermally oxidized toform a thin gate oxide layer 550 having a thickness of from about 50 Åto about 300 Å. A polysilicon layer is then deposited, patterned, andetched to create a gate electrode 555. The surface of the polysilicongate electrode 555 can be reoxidized to form an insulating dielectriclayer 560, providing the structure shown in FIG. 5A.

Referring to FIG. 5B, the source and drain regions 570A,B are nextformed by doping the appropriate regions with suitable dopant atoms. Forexample, on p-type substrates 525, an n-type dopant species comprisingarsenic or phosphorous is used. Typically the doping is performed by anion implanter and might include, for example, phosphorous (³¹P) at aconcentration of about 10¹³ atoms/cm² at an energy level of from about30 keV to about 80 keV, or arsenic (⁷⁵As) at a dose of from about 10¹⁵to 10¹⁷ atoms/cm² and an energy of from 10 keV to 100 keV. After theimplantation process, the dopant is driven into the substrate 525 byheating the substrate, for example, in a rapid thermal processing (RTP)apparatus. Thereafter, the oxide layer 550 covering the source and drainregions 570A,B is stripped in a conventional stripping process to removeany impurities caused by the implantation process which are trapped inthe oxide layer, providing the structure shown in FIG. 8B.

Referring to FIGS. 5C-5D, a silicon nitride layer 575 is deposited onthe gate electrode 555 and the surfaces on the substrate 525 bylow-pressure chemical vapor deposition (LPCVD) using a gas mixture ofSiH₄, Cl₂, and NH₃. The silicon nitride layer 575 is then etched usingreactive ion etching (RIE) techniques to form nitride spacers 580 on thesidewall of the gate electrode 555, as shown in FIG. 5D. The spacers 580electrically isolate the silicide layer formed on the top surface of thegate 555 from other silicide layers deposited over the source 570A anddrain 570B. It should be noted that the electrical isolation sidewallspacers 580 and overlayers can be fabricated from other materials, suchas silicon oxide. The silicon oxide layers used to form sidewall spacers580 are typically deposited by CVD or PECVD from a feed gas oftetraethoxysilane (TEOS) at a temperature in the range of from about600° C. to about 1,000° C.

Referring to FIG. 5E, a native silicon oxide layer 585 is formed onexposed silicon surfaces by exposure to the atmosphere before and afterthe processes. The native silicon oxide layer 585 must be removed priorto forming conductive metal silicide contacts on the gate 555, source570A, and drain 570B to improve the alloying reaction and electricalconductivity of the metal silicide formed. The native silicon oxidelayer 585 can increase the electrical resistance of the semiconductingmaterial, and adversely affect the silicidation reaction of the siliconand metal layers that are subsequently deposited. Therefore, it isnecessary to remove this native silicon dioxide layer 585 using the dryetch process described prior to forming metal silicide contacts orconductors for interconnecting active electronic devices. The dry etchprocess removes the native silicon oxide layers 585 to expose the source570A, drain 570B, and the top surface of the gate electrode 555 as shownin FIG. 5F.

Thereafter, as illustrated in FIG. 5G, a plasma vapor deposition (PVD)sputtering process is used to deposit a layer of metal 590. Conventionalfurnace annealing is then used to anneal the metal and silicon layers toform metal silicide in regions in which the metal layer 590 is incontact with silicon. The anneal is typically performed in a separateprocessing system. Accordingly, a protective cap layer (not shown) maybe deposited over the metal 590. The cap layers are typically nitridematerials and may contain one or more materials, such as titaniumnitride, tungsten nitride, tantalum nitride, hafnium nitride, andsilicon nitride. The cap layer may be deposited by any depositionprocess, preferably by PVD.

Annealing typically involves heating the substrate 500 to a temperatureof between 600° C. and 800° C. in an atmosphere of nitrogen for about 30minutes. Alternatively, the metal silicide 595 can be formed utilizing arapid thermal annealing process in which the substrate 500 is rapidlyheated to about 1,000° C. for about 30 seconds. Suitable conductivemetals include cobalt, titanium, nickel, tungsten, platinum, and anyother metal that has a low contact resistance and that can form areliable metal silicide contact on both polysilicon and monocrystallinesilicon.

Unreacted portions of the metal layer 590 can be removed by a wet etchusing aqua regia, (HCl and HNO₃) which removes the metal withoutattacking the metal silicide 595; the spacer 580, or the field oxide545A,B, thus leaving a self-aligned metal silicide contact 595 on thegate 555, source 570A, and drain 570B, as shown in FIG. 5H. Thereafter,an insulating cover layer comprising, for example, silicon oxide, BPSG,or PSG, can be deposited on the electrode structures. The insulatingcover layer is deposited by means of chemical-vapor deposition in a CVDchamber, in which the material condenses from a feed gas at low oratmospheric pressure, as for example, described in commonly assignedU.S. Pat. No. 5,500,249, which is incorporated herein by reference.Thereafter, the structure 500 is annealed at glass transitiontemperatures to form a smooth planarized surface.

In one or more embodiments, the processing chamber 100 can be integratedinto a multi-processing platform, such as an ENDURA® platform availablefrom Applied Materials, Inc., located in Santa Clara, Calif. Such aprocessing platform is capable of performing several processingoperations without breaking vacuum. Details of the ENDURA® platform aredescribed in commonly assigned U.S. Ser. No. 09/451,628, entitled“Integrated Modular Processing Platform,” filed on Nov. 30, 1999, whichis incorporated by reference herein.

FIG. 6 is a schematic top-view diagram of an illustrative multi-chamberprocessing system 600. The system 600 can include one or more load lockchambers 602, 604 for transferring of substrates into and out of thesystem 600. Typically, since the system 600 is under vacuum, the loadlock chambers 602, 604 may “pump down” the substrates introduced intothe system 600. A first robot 610 may transfer the substrates betweenthe load lock chambers 602, 604, and a first set of one or moresubstrate processing chambers 612, 614, 616, 618 (four are shown). Eachprocessing chamber 612, 614, 616, 618, can be outfitted to perform anumber of substrate processing operations including the dry etchprocesses described herein in addition to cyclical layer deposition(CLD), atomic layer deposition (ALD), CVD, PVD, etch, pre-clean, degas,orientation and other substrate processes.

The first robot 610 can also transfer substrates to/from one or moretransfer chambers 622, 624. The transfer chambers 622, 624 can be usedto maintain ultrahigh vacuum conditions while allowing substrates to betransferred within the system 600. A second robot 630 can transfer thesubstrates between the transfer chambers 622, 624 and a second set ofone or more processing chambers 632, 634, 636, 638. Similar toprocessing chambers 612, 614, 616, 618, the processing chambers 632,634, 636, 638 can be outfitted to perform a variety of substrateprocessing operations including the dry etch processes described hereinin addition to CLD, ALD, CVD, PVD, etch, pre-clean, degas, andorientation, for example. Any of the substrate processing chambers 612,614, 616, 618, 632, 634, 636, 638 may be removed from the system 600 ifnot necessary for a particular process to be performed by the system600.

An illustrative multi-processing system 600 for forming the MOSFETstructure of FIGS. 5A-5H can include two processing chambers 100 asdescribed above, two physical vapor deposition chambers to deposit themetal 500 and two physical vapor deposition chambers to deposit theoptional cap layer (not shown). Any one of the processing chambers 612,614, 616, 618, 632, 634, 636, 638 shown in FIG. 6 represent the PVDchambers and/or processing chambers 100.

Although the process sequence above has been described in relation tothe formation of a MOSFET device, the dry etch process described hereincan also be used to form other semiconductor structures and devices thathave other metal silicide layers, for example, silicides of tungsten,tantalum, molybdenum. The cleaning process can also be used prior to thedeposition of layers of different metals including, for example,aluminum, copper, cobalt, nickel, silicon, titanium, palladium, hafnium,boron, tungsten, tantalum, or mixtures thereof.

To provide a better understanding of the foregoing discussion, thefollowing non-limiting example is offered. Although the example may bedirected to specific embodiments, the example should not be interpretedas limiting the invention in any specific respect.

EXAMPLE

During etch, a gas mixture of 2 sccm of NF₃, 10 sccm of NH₃ and 2,500sccm of argon was introduced into the chamber. A plasma of the gasmixture was ignited using 100 watts of power. The bottom purge was 1,500sccm of argon and the edge purge was 50 sccm of argon. The chamberpressure was maintained at about 6 Torr, and the substrate temperaturewas about 22° C. The substrate was etched for 120 seconds.

During subsequent annealing, the spacing was 750 mil and the lidtemperature was 120° C. The substrate was annealed for about 60 seconds.About 50 Å of material was removed from the substrate surface. No annealeffect was observed. The etch rate was about 0.46 Å per second (28Å/min). The observed etch uniformity was about 5% for the 50 Å etch.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties, reaction conditions, and so forth, used in thespecification and claims are to be understood as approximations. Theseapproximations are based on the desired properties sought to be obtainedby the present invention, and the error of measurement, and should atleast be construed in light of the number of reported significant digitsand by applying ordinary rounding techniques. Further, any of thequantities expressed herein, including temperature, pressure, spacing,molar ratios, flow rates, and so on, can be further optimized to achievethe desired etch selectivity and particle performance.

While the foregoing is directed to embodiments of the invention, otherand further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method for removing silicon oxides from a substrate surface,comprising: positioning a substrate comprising exposed silicon oxide ina first position within a processing chamber, the first position spaceda first distance from a gas distribution plate coupled to the chamber;generating a plasma of reactive species from a gas mixture within theprocessing chamber; contacting the exposed silicon oxide on thesubstrate with reactive species while forming a film on the substrate ata first temperature of less than about 65° C.; moving the substrate intoa second position within the processing chamber, the second positionlocated a second distance from the gas distribution plate, the seconddistance being less than the first distance; and heating the substrateto a second temperature of about 100° C. or greater within theprocessing chamber at the second position to sublimate the film.
 2. Themethod of claim 1, wherein the film comprises ammoniumhexafluorosilicate.
 3. The method of claim 1, wherein the gas mixturecomprises ammonia, nitrogen trifluoride, and a carrier gas.
 4. Themethod of claim 3, wherein the gas mixture comprises a total volume ofthe ammonia and the nitrogen trifluoride within a range from about 0.05%to about 20%.
 5. The method of claim 1, wherein the first temperature isabout room temperature or less.
 6. The method of claim 5, wherein thefirst temperature is about 22° C. or less.
 7. The method of claim 1,wherein the first temperature is within a range from about 15° C. toabout 50° C.
 8. The method of claim 7, wherein the first temperature iswithin a range from about 22° C. to about 40° C.
 9. The method of claim1, wherein heating the substrate comprises positioning the substrateadjacent a heated gas distribution plate disposed within the processingchamber.
 10. The method of claim 9, wherein the second temperature iswithin a range from about 115° C. to about 200° C.
 11. The method ofclaim 9, wherein the second temperature is about 120° C.
 12. The methodof claim 9, wherein the second position is located within a range fromabout 10 mils to about 200 mils from the heated gas distribution plate.13. The method of claim 1, wherein the gas mixture comprises a molarratio of ammonia to nitrogen trifluoride of at least 3:1.
 14. The methodof claim 13, wherein the molar ratio of ammonia to nitrogen trifluorideis within a range from about 5:1 to about 30:1.
 15. The method of claim1, wherein the gas distribution plate is heated to a temperature withina range from about 100° C. to about 150° C. while heating the substratewithin the processing chamber to sublimate the film.
 16. The method ofclaim 15, wherein the substrate is located from the gas distributionplate a distance within a range from about 10 mils to about 200 mils.17. A method for removing silicon oxides from a substrate surface withina processing chamber, comprising: generating a plasma of reactivespecies from a gas mixture within the processing chamber, wherein theplasma comprises ammonium fluoride or ammonium hydrogen fluoride;exposing a silicon oxide surface on a substrate located in a firstposition to the plasma at a first temperature of less than about 65° C.while forming a film comprising ammonium hexafluorosilicate, the firstposition spaced a first distance from a gas distribution plate coupledto the chamber; heating the gas distribution plate within the processingchamber; positioning the substrate in a second position, the secondposition located a second distance from the gas distribution plate, thesecond distance being less than the first distance and within a rangefrom about 10 mils to about 200 mils from the gas distribution plate;and heating the substrate to a second temperature of about 100° C. orgreater within the processing chamber at the second position tosublimate the film.
 18. The method of claim 17, wherein the gas mixturecomprises ammonia, nitrogen trifluoride, and a carrier gas.
 19. Themethod of claim 18, wherein the gas mixture comprises a total volume ofthe ammonia and the nitrogen trifluoride within a range from about 0.05%to about 20%.
 20. The method of claim 17, wherein the first temperatureis about 22° C. or less.
 21. The method of claim 17, wherein the firsttemperature is within a range from about 15° C. to about 50° C.
 22. Themethod of claim 21, wherein the second temperature is about 120° C. 23.The method of claim 17, wherein the gas mixture comprises a molar ratioof ammonia to nitrogen trifluoride of at least 3:1.
 24. The method ofclaim 23, wherein the molar ratio of ammonia to nitrogen trifluoride iswithin a range from about 5:1 to about 30:1.
 25. A method for removingsilicon oxides from a substrate surface, comprising: supporting asubstrate in a first position, the substrate comprising a silicon oxidesurface within a processing chamber, the first position spaced a firstdistance from a gas distribution plate coupled to the chamber;generating a plasma of reactive species from a gas mixture within theprocessing chamber, wherein the gas mixture comprises ammonia, nitrogentrifluoride, and a carrier gas and the gas mixture comprises a totalvolume of the ammonia and the nitrogen trifluoride within a range fromabout 0.05% to about 20%; cooling the substrate to a first temperatureof less than about 65° C. within the processing chamber; exposing thesilicon oxide surface on the cooled substrate to reactive species whileforming a film on the substrate; moving the substrate to a secondposition within the processing chamber, the second position located asecond distance from the gas distribution plate, the second distancebeing less than the first distance; and heating the substrate to asecond temperature of about 100° C. or greater within the processingchamber to sublimate the film.
 26. The method of claim 25, wherein thesecond temperature is within a range from about 115° C. to about 200°C., and the operating pressure within the chamber is within a range fromabout 500 milliTorr to about 30 Torr while heating substrate.
 27. Themethod of claim 26, wherein the second distance is within a range fromabout 10 mils to about 200 mils from the gas distribution plate.
 28. Themethod of claim 27, wherein the first temperature is within a rangebetween about 22° C. and 40° C., and the second temperature is within arange from about 115° C. and 200° C.